The line `A x+B y+C=0` cuts the circle `x^2+y^2+a x+b y+c=0` at `Pa n dQ` . The line `A^(prime)x+B^(prime)x+C^(prime)=0` cuts the circle `x^2+y^2+a^(prime)x+b^(prime)y+c^(prime)=0` at `Ra n dSdot` If `P ,Q ,R ,` and `S` are concyclic, then show that `|a-a ' b-b ' c-c ' A B C A ' B ' C '|=0`